Purification of alcohols obtained from olefines



A. H. BUMP May 11, 1937.

4PURIFICA'IION OF ALCOHOLS OBTAINED FROM OLEFINES Filed May 28, 1954 ZZDAOO UZH WHHUHM .HODQOMLM AOTMOUQKN $0@ .HO 10 UWW Il mmzlll MHSHH Patented May '11, 1937 PURIFICATION F yALCQHOLS OBTAINED FROM OLEFINES Albert H. Bump, Watertown, Mass., assig'nor, by`

mesne assignments,

Company, a corporation of Delaware to Monsanto Chemical Apiiication May 2s, 1934, serai No. '127,964l

l2 Claims.

This invention relates to the manufacture of aliphatic alcohols which are derived from normally gaseous olefines, such as ethyl, isopropyl and isobutyl alcohols, and it has particular ap- 5 plication to the purification of such alcohols to remove impurities commonly associated With alcohols obtained from olenes of cracked petroleum origin. y i

The manufacture of alcohols from normally gaseous olenes is Well known. Various methods for effecting this conversion have been proposed, including the direct or catalytic hydration of olenesand the indirect hydration wherein the oleine is rst combined with an inorganic acid, such as sulphuric acid, to form an ester, that subsequently is hydrolyzed tomregenerate the free inorganic acid and produce the alcohol corresponding tothe olene orolenes which previously were combined withthe acid to form the ester.

, One objectl of the 'present invention is to provide a method of rpurifying alcohols obtained from olenes by which the quality attained is comparable to the best grade of alcohol obtainable by the well known fermentation processes and which may be utilized for purposes such as cologne spirits and the like. c

A further object of the present invention is to provide a method of purification which is ccnveniently adapted to present day alcohol rening equipment and economical aswell as efcient to operate.

A further and inore'specic object of the'present invention is to provide a method of producing cologne spirits derived froinethylene' of a cracked hydrocarbon origin, in which the ethylene has been combined with sulphuric acid to form an ethyl sulphate ester mixture, richl in diethyl sul-V phate.

Although alcoholsobtained from olenes and .i0 reiied by ordinary methods are satisfactory for some purposes where the( purity is of minor con- Isequence or where the product is not obtainable by other competitive processes. for most purposes the alcohol is unsatisfactory. This is par- (Cl. IN2-57) And, finally, in part they are ci' an alcohols by ordinary methods of distillation or' i fractionation, and they impart a foul, undesirable odor to the alcohol characteristic of the crude olefine gases such 'as'ar'obtained in the' cracking of petroleum hydrocarbons and which may be recognized as a'lfoul or sour gasoline odor.)

When an alcohol such as ethyl alcohol, that has been derived from a cracked petroleum Vole-`` ne, is puried by the ordinary methods of fractionation and distillation, the quality thereof is improved somewhat so far as the aldehydic imf purities are concernedfbut the lvolatile hydro carbon impurities remain, and regardless of the number oi' times the material is distilled the characteristic odor persists to such an extent as i j to render the product of no value for competitive marketingpurposes. Small amounts of "hydro-` carbon impurities in alcohol as refined above E are recognized by the following tests:

A: 2-10 ce. of 95% alcohol are poured into about 50 cc. of distilled water which is at a temperature of 60 C.--'l0 C. Immediately thereafter a foul odor is evolved which is reminiscent of sour gasoline.

B: About 10 cc. of the 95% alcohol is added to a test tube containing 2 cc. of water white C. P. sulphuric acid (specific gravity V1.835), the alcohol and acid both vbeing at room temperature. The tube is shaken to obtain thorough mixing of the constituents. Depending upon the amount of the hydrocarbon impurities present, the solution becomes colored, the color ranging from a delicate lavender to a deep pink. Depending also on theamount of hydrocarbon, the time required for the development of the colorvaries from va few seconds to several hours.

Tests A and B are referred to hereinafter as the odor test and the sulphuric acid test, respectively. A satsfactorily puried alcohol gives no odor test nor will a positive sulphuric acid test be obtained even after the alcohol-sulphuric acid mixture is aged several days.

C: 'Ihe 95% spirit when diluted with 20 to 50 volumes of cold water becomes faintly milky or opalescent due. in all probability to the separation of the hydrocarbon which is soluble in the concentrated alcohol but which is immiscible with water or very dilute alcohol.

It has already been indicated that one of the specic objects of the invention is to provide a method of purifying ethyl alcohol obtained from ethylene of a cracked petroleum origin, which ethylene has been converted to an ethyl sulphate ester rich vin the diethyl sulphate form. It is with one mol. of sulphuric acid the half ester Y or ethyl acid sulphate is formed. Upon hydrolysis, the half ester produces only one mol. of alcohol and one mol. of sulphuric acid. It is evident, therefore, that to obtainthe most efilcient use of the acid one should press the combination of ethylene and sulphuric acid to the diethyl sulphate form as far as practicable. One of the limiting factors in this direction is the quality of the alcohol obtained. Thus, when one or less than one mol. of ethylene is combined with one mol. oi' sulphuric acid, an alcohol which is comparatively easy to reilne is obtained. When substantially more than one mol. of ethylene is combined with one mol. of sulphuric acid, the conditions of the reaction being more drastimthe qualityof the alcohol obtained is markedly inferiorand more diilicult to rene due to excessive amounts of "hydrocarbon impurities. By means of the present invention this factor is for practical purposes -obviated insofar as it bears upon the amount of ethylene which can economically be combined with a given amount oi' sulphuric acid, and it therefore enables one to operate the alcohol process, as a whole, more economically and advantageously.

It is to be understood that the mixture of ethyl esters obtained when ethylene is combined with sulphuric acid varies and that even under .the most favorable conditions it is impractical to obtain a complete conversion of sulphuric acid to diethyl sulphate. In the absence of catalysts a typical sulphate ester mixture, which is high in the amount of ethylene absorbed, will consist of 60% by weight of diethyl sulphate, 30% of ethyl acid sulphate, and 10% free sulphuric acid.

'Ihe method by which the sulphate ester mixture is hydrolyzed and the alcohol recovered forms no part of the present invention. Any desired procedure for effecting this hydrolysis and recovery of alcohol may be employed.

When an ethyl sulphate mixture is hydrolyzed and the alcohol is recovered therefrom, as by distillation, one obtains an ethyl alcohol mixture of approximately 50% by weight or less. The mixture contains one to four or even more per cent by weight of diethyl ether, small amounts of sulphur dioxide, acetaldehyde, immiscible high boiling hydrocarbon oils, and the comparatively lower boiling, foul smelling "hydrocarbons" in solution.

When an anhydrous alcohol product is not de sired or required, I prefer to eliminate the impurities by an alternative procedure, which is based on the observation that the hydrgarbon" impurities are separable from alcohol by distillation under conditions which enable one to remove the same as a ternary mixture of water, alcohol and hydrocarbon." To this end the crude aqueous alcohol, obtained upon hydrolysis and distillation of the ethyl sulphate, is adjusted to a concentration of approximately 40% alcohol by weight. Lower alcohol' concentrations are operative although they entail higher subsequent rectifying costs. Substantially higher concentrations give inferior results which can be oiset in part by adding more water at the top of the column. Suiiicient caustic soda is added to the alcohol to bring the pH of the mixture to approximately nine or preferably ten as determined by the Hellige-Klett hydrogen ion comparator. This degree of alkalinity appears to function most satisfactorily so far as hydrocarbon elimination and the economies of process are concerned. A higher concentration of caustic may be employed, although in general this does not improve the results. A lower pH concentration may be employed insofar as the elimination of the sulphur dioxide is concerned, but with a pH of seven or even eight the removal of hydrocarbon impurities is not as satisfactory. In general, a pH value less than five will result in a small amount of the sulphur dioxide being carried over into the rened alcohol. The more expensive caustic potash may be employed but no commensurate advantages are gained thereby. Soda ash and potash are satisfactory substitutes for caustic soda to'promote hydrocarbon elimination, although they lack to some degree the resinifying action of caustic soda upon aldehydic impurities, if any. The crude distillate so treated is then fed continuously to the appropriate plate of a stripping column of the usual commercial design employed in grain and molassesI Percent Alcohol 60 Diethyl ether 30 Water 8-10v Soluble "hydrocarbon" and other impurities 2 Obviously, the foregoing proportions may be varied widely, the one limitation being that the soluble hydrocarbon impurities shall be removed as a ternary mixture, leaving dilute aicohol to be withdrawn from the base of the column. 'I'he alcoholic liquid discharged from the base of the aldehyde column is essentially free of all low boiling and otherwise inseparable hydrocarbon impurities, and is fed continuously to a rectifying column of standard design. By operating this rectifying column in the usual manner with regard to throughput and reiiux ratio, an alcohol of 95% is readily obtained, which is entirely free of malodorous hydrocarbons, which gives a negative sulphuric acid test, and which otherwise is equal to a good market grade of spirits. that is middle run molasses alcohol or grain alcohol, and finally, no fusel oil is present. By the usual method of double distillation common in grain or molasses alcohol manufacture. ethyl alcohol derived from ethylene of cracked petroleum origin and refined by the foregoing method may be converted to the best grade of cologne spirit.

The small quantity of non-miscible, high boiling hydrocarbons are separated and withdrawn from the rectifying column in the same manner as fusel oils from molasses or grain alcohol. These hydrocarbons are non-miscible in the crude and are not nearly as malodorous as the low boiling hydrocarbons which are soluble in the 40% crude alcohol.

'I'he head fraction obtained in the stripping column consists of a mixture of an alcohol, ether, water and the malodorous hydrocarbons. The amount of alcohol therein is equivalent to approximately 10%-45% of the pure alcohol produced. To recover this alcohol the distillate is diluted with water until the weight ratio of alcohol to water is approximately 3:7. The ether is then recovered by distillation in a batch still provided with a fractionating column, after which the ether free alcohol of approximately 30% strength is cooled to 25 C.35 C. and agitated with such activated decolorizing charcoal as "Nuchar. For this purpose 8-10 grams of char coal and A10-12 grams of filterai-d (i. e. diatoma ceous earth) will be found sufficient for each gallon of 30% alcohol treated. After agitating the mixture for about thirty minutes the charge is filtered and the clear alcoholic solution, which is largely freed of malodorous hydrocarbons. is returned to the crude alcohol storage where it is combined with a subsequent charge of alcohol, treated with caustic soda and in this manner l reprocessed with fresh crude alcohol. The forewise to be understood that the dilution of the alkaline alcohol which is stripped to remove the vhydrocarbon impurities as a ternary mixture of alcohol, water and hydrocarbon may be varied. In general, I have found that a 40% alcohol is sumciently dilute to afford rapid and complete removal of the hydrocarbon while at the same time excessive subsequent rectification costs are avoided. In general, I have found that a '40% alcoholic solution, having a pH of approximately I0 is readily stripped of the hydrocarbon impurity. but as indicated heretofore these conditions may be varied and the principles of my invention are not limited, to any specic set of conditions.

Although I have described my invention as applied to ethyl alcohol, it is to'be understood that it is applicable in like .manner-sto isopropyl alcohol and with a considerable degree of success to the butyl alcohols.

'I'he accompanying ow sheet shows diagrammatically the directions of flow of the various liquids in the present process.

What I claim is:

1. In the method of purifying alcohols selected from the group ethyl1 butyl, propyl' and derived from oleilnes of a cracked hydrocarbon origin, which alcohols contain a hydrocarbon impurity suggestive of sour gasoline, which includes the steps of rendering the alcohol alkaline and then distilling the hydrocarbon impurity from said alkaline alcohol as a ternary alcohol-hydrocarbon-water mixture while retaining the main volume of alcohol in liquid phase until removal oi the impurity is completed.

2. The method as defined in claim 1 and further characterized in that the alcohol which has been stripped of the hydrocarbon impurity is then rectified.

3. The method as deiined in claim 1 and further characterized in that the distillate obtained during the stripping operation is treated with` an adsorptive agent such as charcoal, Nuchar, or

other adsorptive carbon, whereby a substantial amount of the impurity is eliminated and an alcohol product obtained thereby which is returned to the process-without resulting in an accumula tion of hydrocarbon impurities in the system.

4. The method as defined in claim l and further characterized in that a water soluble alkali is present in the alcohol undergoing the stripping operation in an amount sufiicient to produce a pH value of at least 8.

5, 'I'he method as defined in claim l and further characterized in that a caustic alkali is present in suillcient amount to produce a pH value of at least 8.

6. The method as defined inclaim 1 and further characterizedV in that a caustic alkali is present in Vsuiilcient amount to produce a pH value of approximately 10.

7. 'Ihe method as defined in claim 1 and further characterized in that the alcohol undergoing the stripping operation is not substantially more concentrated thany approximately 40%.

8. The method as dened in claim 1 and further characterized in that the alcohol undergoing the stripping operation is not substantially more concentrated than 40% and the pH value is approximately 10. I

9. 'Ihe method as defined in claim 1 and further characterized in that water is added to the top of the stripping column to facilitate the elimination of the hydrocarbon impurity.

10. The method as defined in claim 1 and further characterized in that water at a temperature of approximately '10 C.'75 C. is added to the top of the stripping column to facilitate the elimination of the hydrocarbon.

11. The method as dennen in claim 1 and fur` column is such that the distillate contains water and alcohol in the ratio of approximately 6:1.

ALBERT H. BUMP. 

